Ten cards each. Group them into melds: three or four of a kind, or three or more in a row of one suit. Cards not in a meld are deadwood — court cards count ten, aces one.
Light moves first: take the face-up upcard or pass. If both pass, Light draws from the stock.
Each turn, draw from the stock or the discard pile, then discard one card. You may not discard the card you just took from the discard pile.
Knock when your deadwood is 10 or less: your opponent may lay off deadwood onto your melds, then you score the difference. Going gin (no deadwood) scores 25 plus all their deadwood, with no layoffs.
If the defender's deadwood is equal or lower, they undercut and score 25 plus the difference. A hand with only two stock cards left is a draw. First to 100 wins.
Pass and play hides each hand until that player taps I'm ready. Games save automatically.
Keyboard: Tab to a card, Enter or Space to select it, then Discard or Knock.